The invention relates to a wide-band branch line coupler, in particular for operation in the microwave and millimeter wave range, which, as a so-called double symmetrical four port coupler matched on all sides, distributes a signal fed in by a first port in any ratio that is constant over the entire bandwidth to a second and third port with a phase difference of 90.degree., so that no power emanates from the remaining fourth port, i.e., it is isolated.
U.S. Pat. No. 4,305,043 to Ho et al. and No. 4,371,982 to Hallford show microwave branch line couplers.